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1.
Heat conduction, convection and radiolysis of the
The calorimeter allows the water absorbed dose, a measure of radiotherapy, to be measured according to its definition. Different detector types are used in the PTB calorimeter; this paper discusses heat conduction, convection and the radiolysis of the
system for a ‘sealed’ detector. The ‘sealed’ detector allows the calorimeter to be operated at room temperature in the case of 60Co-γ-radiation. 相似文献
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2.
金属硫蛋白(Metallothioneins,简称MTs)是一类富含巯基和金属的低分子量蛋白质,广泛存在于哺乳动物中.MTs 通常含61个氨基酸,其中20个为半胱氨酸,不含芳香族氯基酸和组氨酸,因此在280nm 附近没有吸收峰.MTs 通常结合7个Cd 或zn,20个巯基全部去质子化并参与配位,从而形成牢固的结构域.有证据表明MTs 可能有储存Zn 和Cu 的作用,同时能减轻重金属对动物细胞的毒性,但其生理功能一直不很清楚.近几年的研究表明,MTs 能增强机体对电离辐射的耐受力、修复DNA 损伤,这可能与MTs 中含有丰富的巯基有关.体外实验测得k_(MT/OH)=10~(12)dm~3·mol~(-1)·s~(-1),k_(MT/O(?))=5×10~5dm~3·mol~(-1)·s~(-1),但其辐解机理尚不清楚.本工作利用脉冲辐解技术研究了免肝MT-I 稀水溶液辐解时的中间过程,并作了初步的解释. 相似文献
3.
Transmission electron microscopy is undoubtedly an indispensable tool for materials characterization, which can currently reach sub-angstrom resolution down to the elemental building blocks of matter, isolated single atoms of most elements. In addition to the phenomenal image resolution, if the material is strong enough, it can be accompanied with chemical information, converting electron microscopy into a unique method for the analysis of a great variety of materials. Unfortunately, extracting all this valuable information is not simple as most materials in one way or another are affected by the strong and localized electron beam. Radiolysis is one kind of reaction between electrons and matter than can cause irreversible structural transformations in our materials. This effect is the predominant factor in zeolites, zeotypes and the majority of molecular sieves. In the present work some results, taken at high voltage (300 kV) and minimizing the exposure to the beam, are presented proving the feasibility of the technique to obtain unprecedented atomic resolution information of different zeolites and microporous solids. 相似文献
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5.
张怀钦 《核聚变与等离子体物理》1989,9(3):168-171
本文介绍一个用来测量中子辐照锂化合物产生的氚氢(HT)和氚水(HTO)系统。包括工作原理、操作步骤及初步实验结果。 相似文献
6.
The registration properties of PTFE-E (F-40, Russia; Tefzel, DuPont, USA; Hostaflon ET, Germany) having exceptional chemical and thermal (about 300°C) resistance are considered. The polymer samples were irradiated with ions in a wide region of masses (from O up to Xe) and energies (from 1 to 6 MeV/amu). Alkaline KMnO4 solutions at 100°C were used for etching. It is shown that the polymer registration properties depend on the hydrogen content in the polymer. For a copolymer with 2–3 wt% of hydrogen the registration threshold is about 8 MeVcm2/mg. The ion tracks were not found after chemical etching for a copolymer with 1 wt% of hydrogen. Track membranes were produced and examined. 相似文献
7.
三烷基氧膦是用于高放废液处理的萃取剂,本文试验了在辐照剂量为1×10^4Gy-1×10^6Gy时TRPO损失率。结果表明,100%(V/V)TRPO在λ辐照剂量10^4Gy-10^6Gy变化时,辐解损失率为1.2%-1.6%;30%(V/V)TRPO-煤油在辐照剂量10^4Gy-10^5Gy时,辐解损失率基本不变(0.33%-0.34%),而在1×10^6Gy时增加到0.77%。均低于磷酸三丁酯的 相似文献
8.
主要考察了辛基(苯基)-N, N-二异丁基胺甲酰基甲基氧化膦(CMPO)在1-乙基-3-甲基咪唑双三氟甲基磺酰胺酸盐([C2mim][NTf2])中的γ辐解行为,同时考察辐射对CMPO/[C2mim][NTf2]萃取能力的影响。通过超高效液相色谱-四极杆飞行时间质谱联用仪(UPLC/Q-TOF-MS)进行定量分析、辐解产物认定以及产物半定量分析。CMPO/正十二烷作为对比条件进行了相同研究。结果表明:CMPO在[C2mim][NTf2]中的辐解率低于其在正十二烷中,并且辐解路径不同。在正十二烷体系中,CMPO主要发生C―P、C―N键的断链,而在离子液体体系中CMPO主要发生异丁基脱除反应,并与[C2mim]+·、·CF3等离子液体产生的自由基发生取代反应。综合辐解研究结果,我们提出CMPO/[C2mim][NTf2]的辐解路径,这加深了CMPO在离子液体中辐解机理的认识。最后,通过萃取实验发现,当硝酸浓度为0.01 mol·L-1,辐照剂量为800 kGy时,CMPO/[C2mim][NTf2]对Eu3+的萃取率依旧达到99%以上。 相似文献
9.
Bernard J. Lyons 《Radiation Physics and Chemistry》1993,42(1-3)
This paper describes the effect of an antioxidant, a monomer and fillers (silica or carbon black), alone or in certain combinations with each other, on the mechanical and chemical response of a low density polyethylene to exposure to ionizing radiation. If chain scission is a significant factor in the radiolysis of a polymer, then the relation between sol fraction and Young's modulus or ultimate elongation (both at 160°C) should change depending on whether an additive inhibits or enhances crosslinking. Such additives do not significantly or consistently alter the relation between these properties in a low density polyethylene, indicating that chain scission is not a significant feature of the radiolysis of this polymer. 相似文献
10.
Research on the radiolysis of vitamins is of considerable interest since these compounds are important nutritional constituents in foods and in dietetic supplements. In spite of these considerations there are few data and very often difficult to compare for the radiolytic behavior of vitamins. In this work we focused our attention on to the study of the radiolysis of cyanocobalamin (vitamin B12) in solid state and in aqueous solutions. The procedure was followed by HPLC and UV-spectroscopy. The results obtained in aqueous solutions showed a dependence of the decomposition as a linear function of the dose. The G of decomposition for a 1×10−5 M solution was 3.3. In the solid state the vitamin was very stable towards the irradiation in the conditions used in this study with a G=2.1×10−3. A study made with Serratia marcescens as a microbiological contaminant showed that at the sterilization dose there is a destruction of the vitamin in aqueous solution. In the solid state the degree of decomposition was 7%. 相似文献